I was able to get Zowie an appointment at the v-e-t for tomorrow after work. I came home to find poop on the carpet, but I'm almost 100% certain that it wasn't Zowie, as she has always gone in the box. Also, Pandora's been acting crankier today, so it might be that the Wellness Chicken & Herring upset her tummy. (She almost always will poop outside the box if she has tummy upset.)
I also came home to a big grey hairball on the hardwood, and I'm wondering if that's why Zowie's been not feeling well. I didn't see any diarrhea in the boxes, so either Zowie hasn't gone yet today, or she did a regular visit.
Both Pandora and Zowie got pumpkin mixed in with their canned food this evening, so I'm hoping that'll help a bit.
I'll update you on the v-e-t appointment tomorrow evening. :) Thank you for all the purrs and prayers!